What is the correct definition of life?

[Delta1212]

Alright, then here is a question: Is a DNA molecule alive?

 

DNA replicates itself and "has" DNA.

 

So does DNA, all by itself, qualify as being a form of life?

[koti]

Alright, then here is a question: Is a DNA molecule alive?

 

DNA replicates itself and "has" DNA.

 

So does DNA, all by itself, qualify as being a form of life?

No Delta1212. Please answer my question first.

[Delta1212]

Strange already explained that statement. There is no particular reason to expect aliens to use the specific molecule that Earth life uses to store our genetic code, especially when there are other potential molecules that we are aware of, such as RNA, that are capable of serving an analogous purpose. And when I made that statement I was responding specifically to the post where you said "having DNA" would make for an adequate requirement, not "DNA or something similar.

 

Now, if DNA does not qualify as life, but meets the entirety of "having DNA or something DNA-like and reproducing itself" but, according to you, is not a form of life, then your definition is faulty.

 

A good definition of any category includes everything that is in the category and excludes everything that is not. If you have a definition that does not cover something that should be considered life, or that includes something that is not life, it is not a good definition of life.

[koti]

My definition migh very well be faulty, I know as much about DNA as you about armwrestling (probably an exageration) but flawding my definition of life on the basis of alien life doesnt seem wise. If we find alien life one day (which I very much hope we will) and my definition of life would become obsolete then so be it. By the way, I am also overwhelmed by your unsureness of a sterile specimen being considered life or non-life. I have a female friend who is sterile and its beoyond me how could anyone even think about stating a question like that.

[StringJunky]

I think I said somewhere earlier: the fact that the progression from the non-living to the living is a continuum, renders a nice, tidy definition unlikely.

[dimreepr]

Is there any matter considered non-living that can reproduce?

 

 

Viruses.

[Delta1212]

My definition migh very well be faulty, I know as much about DNA as you about armwrestling (probably an exageration) but flawding my definition of life on the basis of alien life doesnt seem wise. If we find alien life one day (which I very much hope we will) and my definition of life would become obsolete then so be it. By the way, I am also overwhelmed by your unsureness of a sterile specimen being considered life or non-life. I have a female friend who is sterile and its beoyond me how could anyone even think about stating a question like that.

I did not say anything negative about your friend. I pointed out that your proposed definition of life potentially excluded sterile individuals. I was not asking if someone is not alive if they are sterile. I was trying to see whether you saw a problem with excluding those who cannot reproduce from your definition of life. Clearly you do.

 

StringJunky is correct. There is no hard and fast dividing line between life and non-life. This any definition of life is going to be blurry, somewhat arbitrary and to an extent subjective. That means you have to be especially careful about how you build a robust definition of life and any attempt at making a very simple definition is going to carry with it a host of potential problems that need to be considered.

 

You can't dismiss the entire subject as being easy because it is not.

[StringJunky]

Probably, a definition needs to start with acknowledgement of it''s origins from certain unconfigured molecules i'e non-living, and life emerges from them as they become more complex and, ultimately, discretely autonomous.

[Delta1212]

Probably, a definition needs to start with acknowledgement of it''s origins from certain unconfigured molecules i'e non-living, and life emerges from them as they become more complex and, ultimately, discretely autonomous.

Although, frankly, (and this is one of the reasons I favor classifying viruses as life even though they generally aren't) how discretely autonomous any life really is is up for debate.

 

All life exists within an environment outside of which it is incapable of performing the necessary functions of life. We rely on plant life to do the necessary metabolizing of sunlight in order to create the raw materials we require to stay alive. Organisms that rely on sexual reproduction are not equipped to reproduce themselves discretely and males, like viruses, even inject their DNA into a host in order to reproduce themselves.

 

Life is less discrete autonomous organisms and more like waves in the ocean: the water that makes up the wave doesn't move, only the pattern does, discarding and incorporating water molecules as it goes, at once a part of and distinct from its watery environment.

 

But that may be getting a little more philosophical even than the topic already calls for.

[StringJunky]

Although, frankly, (and this is one of the reasons I favor classifying viruses as life even though they generally aren't) how discretely autonomous any life really is is up for debate.

 

All life exists within an environment outside of which it is incapable of performing the necessary functions of life. We rely on plant life to do the necessary metabolizing of sunlight in order to create the raw materials we require to stay alive. Organisms that rely on sexual reproduction are not equipped to reproduce themselves discretely and males, like viruses, even inject their DNA into a host in order to reproduce themselves.

 

Life is less discrete autonomous organisms and more like waves in the ocean: the water that makes up the wave doesn't move, only the pattern does, discarding and incorporating water molecules as it goes, at once a part of and distinct from its watery environment.

 

But that may be getting a little more philosophical even than the topic already calls for.

Yes, that's true - a continuum - but that's just my human need to compartmentalise everything; we draw mental lines around things and say "This is this and that is that".

Edited August 28, 2016 by StringJunky

[koti]

I think I said somewhere earlier: the fact that the progression from the non-living to the living is a continuum, renders a nice, tidy definition unlikely.

This is an interesting alley but I doubt it will render any definition as we are not 100% sure of the process. Also...hypotheticaly even if we had the complete knowledge on the process of the non-life to life progression still I doubt it would help us in this case.

 

 

Viruses.

This is disputable.

And if the sole criteria of life is that it reproduces and has DNA (or equivalent), does that preclude sterile individuals from qualifying as alive? This can be a concern even with traditional definitions of life, but at least there are a range of different characteristics taken into account so there is a bit of wiggle room for individuals that miss one or two traditional categories for one reason or another.

 

I did not say anything negative about your friend. I pointed out that your proposed definition of life potentially excluded sterile individuals. I was not asking if someone is not alive if they are sterile. I was trying to see whether you saw a problem with excluding those who cannot reproduce from your definition of life. Clearly you do.

 

Delta, you are drifting in the middle of an ocean right now, by youreself, naked and with no boat. Your nostrals are being glazed by water and you are choking from time to time and.. it's going to get dark soon.

I suggest we drop this right now.

Edited August 28, 2016 by koti

[swansont]

Isn't this a strawman? - Im refering to Stringjunkies comment.

Strange - Whether we call it DNA or other hypothetical carrier whats the difference?

DNA is a specific molecule. It literally can't be anything different.

[koti]

DNA is a specific molecule. It literally can't be anything different.

On top of the fact that I never questioned that, I also admitted it in one of my comments above.

?

[StringJunky]

There is no inherent meaning of life, life occurred through natural processes and conditions.

 

Though this shouldn't devalue our lives, but rather empower them, rejoice in the fact that at this moment, you exist, because million years ago, stars died (as they all do eventually) spilling their chemically enriched contents out in cosmos, forming planets, including ours. Those very same elements make up your body. You are star stuff, we are all star stuff, and for a brief moment, amidts the chaos, through billions of years, those elements coalesced to form you. Our time in this planet is limited, love those who are around you, cherish it, savour it.

Although what you have written is true and well put together, with one little error, this discussion is about how do we define life, as distinct from non-living things i.e. what is the minimum list of things that describes all living things and makes them separate from those things not living? At the moment, you have misinterpreted the question as a philosophical one about life's purpose for each of us.

Edited August 28, 2016 by StringJunky

[Ophiolite]

But right now do we even have a good theory of life? Do we know what differentiates living things from non-living (or inanimate) things?

 

After searching Wikipedia I have seen many different branches and outlines of biology and the life sciences but what I have not been able to find is a good and working general theory of what life really is.

The vast majority of the research in biology and all its branches being undertaken by thousands of researchers does not require a definition of life, nor does it suffer from the absence of one. This portion of your OP suggests that our knowledge of life is seriously limited. The depth and breadth of our current understanding suggests otherwise.